package com.hmdp.service.impl;

import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import com.hmdp.dto.Result;
import com.hmdp.entity.Shop;
import com.hmdp.mapper.ShopMapper;
import com.hmdp.service.IShopService;
import com.hmdp.utils.CacheClient;
import com.hmdp.utils.RedisConstants;
import com.hmdp.utils.RedisData;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

import javax.annotation.Resource;
import java.time.LocalDateTime;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;

/**
 * <p>
 * 服务实现类
 * </p>
 *
 * @author 虎哥
 * @since 2021-12-22
 */
@Service
public class ShopServiceImpl extends ServiceImpl<ShopMapper, Shop> implements IShopService {

    @Resource
    private StringRedisTemplate stringRedisTemplate;

    @Resource
    private CacheClient cacheClient;

    private static final ExecutorService CACHE_REBUILD_EXECUTOR = Executors.newFixedThreadPool(10);

    @Override
    public Result queryById(Long id) {
        // 缓存穿透
//        Shop shop = cacheClient.
//                queryWithPassThrough(RedisConstants.CACHE_SHOP_KEY,id,Shop.class, this::getById, RedisConstants.CACHE_SHOP_TTL, TimeUnit.MINUTES);

        // 用互斥锁解决缓存击穿
//        Shop shop = queryWithMutex(id);

        //用逻辑过期解决缓存击穿
        Shop shop =
                cacheClient.queryWithPassThrough(RedisConstants.CACHE_SHOP_KEY,id,Shop.class,this::getById,10L,TimeUnit.SECONDS);
        if (shop == null){
            return Result.fail("店铺不存在！");
        }
        // 返回
        return Result.ok(shop);
    }

    //用逻辑过期解决缓存击穿
    public Shop queryWithLogicalExpire(Long id) {
        String key = RedisConstants.CACHE_SHOP_KEY + id;
        // 1.从redis查询商户缓存
        String shopJson = stringRedisTemplate.opsForValue().get(key);
        // 2.判断是否存在
        if (StrUtil.isBlank(shopJson)) {
            // 3.说明未命中，直接返回空
            return null;
        }
        // 4.命中，需要先把json反序列化为对象，然后判断缓存是否过期
        RedisData redisData = JSONUtil.toBean(shopJson, RedisData.class);
        // 因为反序列化时不知道类型是店铺，所以本质上返回了个JSONObject
        JSONObject data = (JSONObject) redisData.getData();
        Shop shop = JSONUtil.toBean(data, Shop.class);
        LocalDateTime expireTime = redisData.getExpireTime();
        // 这个是判断过期时间是不是在当前时间之后，如果是说明未过期
        if (expireTime.isAfter(LocalDateTime.now())){
        // 5.未过期，返回商铺信息
            return shop;
        }
        // 6.过期 需要缓存重建
        // 6.1.获取互斥锁
        String lockKey = RedisConstants.LOCK_SHOP_KEY+id;
        boolean isLock = tryLock(lockKey);
        // 6.2.判断是否获取成功
        if (isLock){
            // 6.3.获取成功，开启独立线程,实现缓存重建
            CACHE_REBUILD_EXECUTOR.submit(()->{
                try {
                    // 缓存重建
                    this.saveShop2Redis(id,20L);
                }catch (Exception e){
                    throw new RuntimeException(e);
                }finally {
                    // 释放锁
                    unlock(lockKey);
                }
            });
        }
        // 6.4.获取失败，返回过期的商铺数据
        return shop;
    }

    // 用互斥锁解决缓存击穿
    public Shop queryWithMutex(Long id) {
        String key = RedisConstants.CACHE_SHOP_KEY + id;
        Shop shop = null;
        // 1.从redis查询商户缓存
        String shopJson = stringRedisTemplate.opsForValue().get(key);
        // 2.判断是否存在
        if (StrUtil.isNotBlank(shopJson)) {
            // 3.存在，直接返回
            return JSONUtil.toBean(shopJson, Shop.class);
        }
        // 判断命中的是否是空值
        if (shopJson != null) {
            // 说明shopJson == ""
            // 返回一个错误信息
            return null;
        }
        // 4.实现缓存重建
        // 4.1 尝试获取互斥锁
        String lockKey = "lock" + id;
        try {
            boolean isLock = tryLock(lockKey);
            if (!isLock) {
                // 4.2 不成功，休眠一段时间并重试
                Thread.sleep(50);
                // 这是重新从redis查询商铺缓存，所以递归调用
                return queryWithMutex(id);
            }
            // 4.3 成功，根据id查询数据库
            shop = getById(id);
            // 模拟重建的延时
            Thread.sleep(200);
            // 5.不存在，直接返回错误
            if (shop == null) {
                //将空值写入redis
                stringRedisTemplate.opsForValue().set(key, "", RedisConstants.CACHE_NULL_TTL, TimeUnit.MINUTES);
                return null;
            }
            // 6.存在，写入redis，然后返回数据
            stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(shop), RedisConstants.CACHE_SHOP_TTL, TimeUnit.MINUTES);
        }catch (Exception e){
            throw new RuntimeException(e);
        }finally {
            // 7. 释放互斥锁
            unlock(lockKey);
        }
        // 8. 返回
        return shop;
    }



    // 缓存穿透的解决方法
    public Shop queryWithPassThrough(Long id) {
        String key = RedisConstants.CACHE_SHOP_KEY + id;
        // 1.从redis查询商户缓存
        String shopJson = stringRedisTemplate.opsForValue().get(key);
        // 2.判断是否存在
        if (StrUtil.isNotBlank(shopJson)) {
            // 3.存在，直接返回
            return JSONUtil.toBean(shopJson, Shop.class);
        }
        // 判断命中的是否是空值
        if (shopJson != null) {
            // 说明shopJson == ""
            // 返回一个错误信息
            return null;
        }
        // 4.不存在，根据id查询数据库
        Shop shop = getById(id);
        // 5.不存在，直接返回错误
        if (shop == null) {
            //将空值写入redis
            stringRedisTemplate.opsForValue().set(key, "", RedisConstants.CACHE_NULL_TTL, TimeUnit.MINUTES);
            return null;
        }
        // 6.存在，写入redis，然后返回数据
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(shop), RedisConstants.CACHE_SHOP_TTL, TimeUnit.MINUTES);
        // 7.返回
        return shop;
    }

    // 获取锁
    private boolean tryLock(String key) {
        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key, "1", 10, TimeUnit.MINUTES);
        return BooleanUtil.isTrue(flag);
    }

    // 释放锁
    private void unlock(String key) {
        stringRedisTemplate.delete(key);
    }

    public void saveShop2Redis(Long id,Long expireTimeSeconds) throws InterruptedException {
        // 1.查询店铺数据
        Shop shop = getById(id);
        Thread.sleep(200);
        // 2.封装逻辑过期时间
        RedisData redisData = new RedisData();
        redisData.setData(shop);
        redisData.setExpireTime(LocalDateTime.now().plusSeconds(expireTimeSeconds));
        // 3.写入redis
        stringRedisTemplate.opsForValue().set(RedisConstants.CACHE_SHOP_KEY+id,JSONUtil.toJsonStr(redisData));
    }
//
    @Override
    @Transactional
    public Result update(Shop shop) {
        Long id = shop.getId();
        if (id == null) {
            return Result.fail("店铺id不能为空");
        }
        // 更新数据库
        updateById(shop);
        // 删除缓存
        stringRedisTemplate.delete(RedisConstants.CACHE_SHOP_KEY + id);
        return Result.ok();
    }
}
